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Adapting Wavelet Compression to Human Motion Capture Clips. Philippe Beaudoin 1 Pierre Poulin 1 Michiel van de Panne 2. 1 Universit é de Montréal, LIGUM 2 University of British Columbia, Imager. A need for compression?. Motion capture is very popular

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adapting wavelet compression to human motion capture clips

Adapting Wavelet Compression to Human Motion Capture Clips

Philippe Beaudoin 1Pierre Poulin 1Michiel van de Panne 2

1 Université de Montréal, LIGUM2 University of British Columbia, Imager

a need for compression
A need for compression?
  • Motion capture is very popular
  • Motion capture rapidly produces huge collections of data
  • Escalating cost of the memory hierarchy (ie. Martin Walker talk)
  • Lossy compression

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

what is a good compression
What is a good compression?
  • Depends on the application
  • We aim for:
    • Small cache footprint
    • Access to subset of joint data
    • Accurate foot placement
    • Independent motion clips
  • Best ratio may not be the target

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

which kind of compression
Which kind of compression?
  • Joint correlation
    • 2:1 up to 4:1 (PCA)
  • Joint + temporal coherence
    • Cannot access individual signals
    • 30:1 up to 35:1 [Arikan 06]
  • Temporal coherence alone
    • 35:1 (this work)
    • Access to subset of joint data
    • Low computational requirements

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

preliminary details
Preliminary details…
  • A pose is…
    • Root position (3 signals)
    • Euler angles of joints (59 signals)
  • Motion is sampled at 120 hz
  • No preprocessing or format conversion before compression

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

standard wavelet compression
Standard wavelet compression
  • Cubic interpolating bi-orthogonal wavelet basis [Sweldens 98]
  • Not specially targeted to motion capture

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

standard wavelet compression1
Standard wavelet compression
  • Wavelet transform 62 signals
  • Keep the largest coefficients from all the transformed signals
  • Yield vector wi (1 ≤ i ≤ 62) counting how many coefficients are kept for each signal

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

slide8

Vector wi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

optimized coefficient selection
Optimized coefficient selection
  • wiminimizes RMS error in the DOF
  • Quality depends much more on positional distortion
  • Optimally redistribute coefficients?
    • Too costly!

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

optimized coefficient selection1
Optimized coefficient selection
  • Motion capture data is hierarchical
  • Build vector mi that favors some signals more than others
  • Fixed choice for mi? Bad!
    • Depends on complexity of signals
    • Depends on the poses

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

slide11

Start withmi = wi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

slide12

Randomly select i reduce mi

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

slide13

Find optimal j increase mj

Repeat…

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

inverse kinematics correction
Inverse kinematics correction
  • Problem: Noticeable sliding feet
  • Change distortion metric?
    • Assumption breaks down, difficult to find a good mi
  • Instead, add positional channels for the feet, use IK

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

inverse kinematics correction1
Inverse kinematics correction
  • Signals encode difference between compressed position and true feet position
  • Wavelet compress these signals independently

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

final details
Final details…
  • Quantize to 16 bits
  • Run-length encode 0s
  • Optionally use lempel-ziv independently on each clip

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

results
Results
  • Tested on 1 sec. to 45 sec. clips
  • Compression ≈ 300 ms/frame
  • Decompression

≈ 30 μs/frame (no IK)

≈ 300 μs/frame (with IK)

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

video
Video

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

conclusion
Conclusion
  • Tractable coefficient search space adapted to motion capture data
  • Fast decompression
  • Access to subset of joints
  • Independent clips
  • 35:1 compression ratio

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

future work
Future Work
  • Metric for perceived quality in a motion capture animation
  • Explore large-scale redundancies (see our technical report)
  • Level-of-detail streaming

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

questions
Questions?

Adapting Wavelet Compression to Human Motion Capture ClipsBeaudoin, Poulin, van de Panne – Graphics Interface 2007

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